Conventional insulated windows employ a plurality of panes of glass which trap air therebetween to serve a thermal insulation function. Prefabricated, elongated hollow spacers, connected in a rectangular frame configuration, are normally placed at the top, bottom and sides of each such air space to physically separate the adjacent panes.
A common problem with multi-glazed windows is that moisture trapped between the adjacent panes condenses on the panes, causing them to become clouded or fogged. Generally, this problem is dealt with by putting desiccant material inside the hollow spacers to absorb the moisture, thereby preventing condensation.
Generally, the prefabricated spacers consist of pieces of elongated sheet metal folded into a hollow cross-sectional shape to define an interior compartment within which the desiccant is contained. Prior to installation, the spacer is sealed at each end with a sealing plug to prevent ambient moisture from coming into contact with the desiccant material. During installation, the spacer is cut to the appropriate size, after which the sealing plugs are replaced with corner pieces inserted in the ends of adjacent spacer members. Each corner piece is formed with a horizontal leg and a vertical leg disposed at a 90.degree. angle, each leg being inserted into the end of one of the adjacent spacers to hold the two adjacent spacers together and in perpendicular relation to one another.
The weakest point of a multiple-glazed window, with respect to moisture leakage, is the corner. The corner pieces generally do not make a moisture-tight seal against the window panes, thereby allowing moisture to leak in and thus significantly reducing the life of the window.
When each leg of the corner piece is inserted into a spacer, a sealing compound is applied around the corner piece and spacers in order to seal any gaps by which ambient moisture could enter. But moisture leakage problems nevertheless arise when, due to changes in temperature and air pressure, the spacers pull away from the corner piece, creating openings through which ambient moisture can enter.
A preferred type of spacer is illustrated in my co-pending patent application Ser. No. 721,796, filed on the same date as this application, entitled "Prefabricated Spacer for Multiple-Glazed Windows." This spacer has a plurality of interior partitions, each formed of a body of moisture-barrier material maintained in a sealing relationship with the interior walls of the compartment. The partitions are spaced at intervals along the length of the spacer, thereby dividing the spacer into subcompartments which each contain desiccant material.
When this type of spacer is cut to a shorter length to accommodate the size of the window, the only desiccant material in the hollow interior which is exposed to ambient moisture is that which is within the particular subcompartment which is cut, thereby minimizing loss of the desiccant. Conventional corner pieces are usually solid metal or plastic bodies with rounded, blunt or squared-off ends. When used with the type of spacer described in my above-mentioned Patent Application, the rounded or blunt ends run up against the partitions. The corner piece then will not be able to fit all the way into the spacer, or may push the partition out of place.